1. Field of Invention
The present invention relates to a dichroic dye and applications thereof, and particularly relates to a liquid crystal composition and a liquid crystal element using the dichroic dye.
2. Description of the Related Art
Many systems have been proposed for liquid crystal elements (liquid crystal display devices). In particular, guest-host liquid crystal elements are expected to serve as liquid crystal elements providing a bright display. A guest-host liquid crystal element includes a dichroic dye dissolved in a liquid crystal, in which the orientation of the dichroic dye changes in accordance with the movement of the liquid crystal under an electric field, thereby changing the light absorption of the liquid crystal element to display an image.
The guest-host system is described in various documents (for example, see Handbook of Liquid Crystals, Vol. 2A, Chapter 3.4, pp. 257-302, written by B. Bahadur, edited by D. Demus, J. Goodby, G. W. Gray, H. W. Spiess, and V. Vill, published by Wiley-VCH, 1998). Dichroic dyes used in guest-host liquid crystal elements are required to have, for example, appropriate absorption properties, high order parameters, high solubility in host liquid crystals, and durability. In order to satisfy these requirements, dichroic dyes having a substituent containing a cyclohexane ring and a structure similar to that of the host liquid crystal have been reported (for example, see Japanese Patent Application Laid-Open (JP-A) No. 58-57488 and JP-A No. 2003-113378).
These patent documents report that a trans-cyclohexane ring exhibits a high order parameter, while a cis-cyclohexane ring significantly decreases the order parameter. However, the trans-cyclohexane ring is not sufficiently soluble in a liquid crystal to provide a high contrast display, and improvement has been required in this regard.